Optimization of a new modified wet-chemistry process for the synthesis of BPSCCO superconductor precursor powders with specific stoichiometry

A modified coprecipitation process has been developed based on a stoichiometry study of the oxalate coprecipitation process in water for the synthesis of Bi-Pb-Sr-Ca-Cu-O multi-component powders. The coprecipitation reaction is carried out in a mixed solution composed of water, ethanol (90 vol%) and pbly(ethylene glycol), thus overcoming the serious shortcoming of water-medium coprecipitation, namely the inability to maintain stoichiometry in Bi-system superconductor powders. The modified process is optimized by the study of the effects of the pH value, oxalic acid concentration and ageing time on stoichiometry maintenance in the precipitate. The precipitation parameters have dramatic effects on the stoichiometry and homogeneity, which in turn affect the superconductivity of a silver-sheathed (Bi,Pb)₂Sr₂Ca₂Cu₃O_x (2223) superconducting tape prepared by the powder-in-tube process. Our results highlight the importance of controlling powder synthesis conditions for obtaining high critical current density (J_c) tape.